In recent years, on a mine site, various types of construction machines have been used; for example, dump trucks are used for haulage. The haulage costs of ores in mines comprise labor costs, fuel costs, maintenance costs, initial investments, or the like, and it is said that the fuel costs take a second largest part after the labor costs. Therefore, it is required to save energy of dump trucks, and various techniques for improving fuel efficiency are suggested.
For example, in Patent Literature 1, a technique is suggested, in which electric power generated by a regenerative braking device and electric power required by an auxiliary device are successively measured and compared, and only when the regenerating electric power exceeds the electric power required by the auxiliary device, a load output of a power generator for auxiliary device is reduced, and the regenerating electric power is simultaneously supplied to the auxiliary device.